I've been looking at current open source 2d animation tools and it doesn't really seem like there's anything that can (or is even attempting to) compete with professional 2d animation tools.

Since Blender is already an excellent cross-platform animation platform with a bunch of great 2d compositing features and the like, it seems like adding 2d animation capabilities would be an ideal fit. I think you would probably want to have 2d vector editing tools that you could then either tween or draw frame by frame (with good onion skinning support); and then you could set the depth of the plane that they're rendered on in the 3d scene. This way it's just rendered as a plane at a specific depth that's always facing the camera (and you could of course have as many at different depths as you want).

In the long term it would be great to see a set of tools that compete with RETAS for traditional animation and something like Flash for smooth computer-tweened 2d. But even if that's an overly optimistic goal, it seems bizarre that there are such well-supported tools for vector creation (Inkscape) and 3d animation (Blender) but nothing that even attempts to rival professional 2d tools.

there is no simple value field for the depth order, but as you said, you can have as many depths as you need by simply changing the z location of an object.

Onion skinning is already supported (for Armatures), see Ghost panel in Properties editor, Armature tab. There is also a more generic variation for Objects called Motion Paths, but i couldn't get this to work for directly animated objects. It worked for constraints though.

2d vector editing tools - not sure what you mean. We got polylines, which can be limited to 2D, and the new masks tools which are basically animatable 2d-splines. Isn't that enough?

I was actually suggesting a new editor (vector-based traditional animation, not computer-tweened) and a bit of the implementation (render to a plane always facing the camera at a specified distance/depth from the camera). I'll certainly admit I haven't looked at everything in Blender, but I would be greatly surprised if there's an easy way to create 2d vector art that you can adjust the fill and stroke on and make completely different each frame.

The vector tools I am suggesting would be similar to what's in RETAS or a pared-down Inkscape if you would prefer. In RETAS you're effectively digitally inking and painting animation cels; from my understanding it's what's used in most anime (there are some good videos on this on Youtube if you want to see specifics).

The real concern would be an easy way to have completely independent hand-drawn frames, not auto-tweened splines between specified keyframes. Basically, I would like to be able to draw animation frame-by-frame on top of / incorporated directly into a 3d scene in Blender.

I am suggesting this as an addition to Blender because:
1) There don't seem to be any good open source traditional animation tools
2) More and more animation is done with a mix of 2d and 3d, so being able to use one program throughout would be beneficial.
3) Blender already does a lot of what you'd want a RETAS competitor to do with the actual layout of scenes and final composition since the 2d components can then be rendered in 3d with various depths and perspectives.

so you wish to get like InkScape with timebased animation, basically an open source 2d vector animation program similar to Flash. Dunno if this really fits into Blender, but could be interesting. But would it render to vector files or image files?

I found this short wiki article, it explains how you can create frame-by-frame animations with InkScape. You may be interested into it:

Sort of; ideally you would be able to do either Flash-esque auto-tweened animation or traditional hand-drawn (or hand-created vectors at least) animation.

Basically, if in a Flash-type mode it would work very similar to a 2d Blender. You would create and position 2d vector objects, keyframe them and be able to adjust the animation curves, etc.

In a 'traditional' mode you would draw each frame that you want separately, as if you were drawing a flip book. Blender would make no attempt to tween or otherwise assist, and individual frames could have an entirely different number of vector objects since they don't have to match between frames. It would effectively be like creating hundreds of images in Inkscape, importing them all into Blender, and animating that element by switching between the different images (but being able to do this directly through Blender which would make this a much faster / more seamless process).

With either method the output would be part of the rendering output. During the render step the vector art would first be effectively rendered to a texture, and that would then be rendered as part of a normal 3d scene on a plane at a specified distance always facing the camera.

As a simple example, say you wanted to do a stick figure fight (a popular topic if YouTube is to be believed) animated within a 3d flythrough of a city street.

Currently you would have to create and animate the 3d scene and then take all the rendered frames and paint the stick figures in each frame (also making sure to composite it correctly taking into account foreground objects that the stick figures should go behind, not in front of). You would also be unable to use certain Blender features such as depth of field with foreground objects if the stick figures are meant to be partially obscured by the blurred foreground.

My proposal would effectively let you draw your frames from within Blender and be rendered as part of the 3d scene, allowing much greater flexibility in compositing 2d and 3d elements.

What Defiant00 is asking for would effectively make Blender a viable replacement for Toon Boom Harmony. Harmony is an extremely expensive, 2D, vector-based animation program in which you can do traditional (or "tradigital") animation as well as IK. Drawing in Harmony is vector based, though, if you want a more "painterly" look for backgrounds, you could import PSDs with layers. You can arrange flat, 2d images in front of each other to simulate depth... similar to what's being done with Blender in this video:

You can import fbx and obj into Harmony, but to render any 3D object you've imported you need Maya installed on your computer.

I'm new to both Maya and Blender and I'm finding Maya to be extremely annoying and much more difficult to learn than Blender (this might just be my issue).

The way I see it there are 2 solutions:
For those who already have Harmony - Someone in the Blender community, who is much smarter than myself, could create plugins for Blender that would allow it to be used by Harmony in the same way Harmony uses Maya,

or

someone who is, again, much smarter than myself, could create a set of features for Blender that mimic Harmony's animation features. That way, everything could be done all in one program.

[quote="NoOneYouKnow"]What Defiant00 is asking for would effectively make Blender a viable replacement for Toon Boom Harmony. Harmony is an extremely expensive, 2D, vector-based animation program in which you can do traditional (or "tradigital") animation as well as IK. Drawing in Harmony is vector based, though, if you want a more "painterly" look for backgrounds, you could import PSDs with layers. You can arrange flat, 2d images in front of each other to simulate depth... similar to what's being done with Blender in this video:

You can import fbx and obj into Harmony, but to render any 3D object you've imported you need Maya installed on your computer.

I'm new to both Maya and Blender and I'm finding Maya to be extremely annoying and much more difficult to learn than Blender (this might just be my issue).

The way I see it there are 2 solutions:
For those who already have Harmony - Someone in the Blender community, who is much smarter than myself, could create plugins for Blender that would allow it to be used by Harmony in the same way Harmony uses Maya,

or

someone who is, again, much smarter than myself, could create a set of features for Blender that mimic Harmony's animation features. That way, everything could be done all in one program.[/quote]

I was thinking the same thing! Did you find any good software? I've been using flipbook a bit but it's very buggy.

[quote="Defiant00"]Sort of; ideally you would be able to do either Flash-esque auto-tweened animation or traditional hand-drawn (or hand-created vectors at least) animation.

Basically, if in a Flash-type mode it would work very similar to a 2d Blender. You would create and position 2d vector objects, keyframe them and be able to adjust the animation curves, etc.

In a 'traditional' mode you would draw each frame that you want separately, as if you were drawing a flip book. Blender would make no attempt to tween or otherwise assist, and individual frames could have an entirely different number of vector objects since they don't have to match between frames. It would effectively be like creating hundreds of images in Inkscape, importing them all into Blender, and animating that element by switching between the different images (but being able to do this directly through Blender which would make this a much faster / more seamless process).

With either method the output would be part of the rendering output. During the render step the vector art would first be effectively rendered to a texture, and that would then be rendered as part of a normal 3d scene on a plane at a specified distance always facing the camera.

As a simple example, say you wanted to do a stick figure fight (a popular topic if YouTube is to be believed) animated within a 3d flythrough of a city street.

Currently you would have to create and animate the 3d scene and then take all the rendered frames and paint the stick figures in each frame (also making sure to composite it correctly taking into account foreground objects that the stick figures should go behind, not in front of). You would also be unable to use certain Blender features such as depth of field with foreground objects if the stick figures are meant to be partially obscured by the blurred foreground.

My proposal would effectively let you draw your frames from within Blender and be rendered as part of the 3d scene, allowing much greater flexibility in compositing 2d and 3d elements.[/quote]